Conventionally, attempts have been made to scale electric and electronic components such as motor and transformer cores to higher densities and smaller sizes and to allow more precise control to be effected using low electric power. This has led to development of soft magnetic materials used in producing such electric and electronic components, particularly soft magnetic materials having superior magnetic characteristics in the middle to high frequency range.
In conjunction with such soft magnetic materials, Japanese Patent Laying-Open No. 2002-246219, for example, discloses a dust core aimed at maintaining magnetic characteristics during use under a high temperature environment, and a method of producing thereof (Patent Document 1). According to the method of producing the dust core disclosed in Patent Document 1, atomized iron powder covered with a phosphate film is first mixed with a predetermined amount of polyphenylene sulfide (PPS resin) and is subjected to a compacting process. The resulting compact is heated in air at a temperature of 320° C. for one hour and then heated at a temperature of 240° C. for another one hour. The compact is then cooled to produce a dust core.
Patent Document 1: Japanese Patent Laying-Open No. 2002-246219